Silicon is an essential nutrient for plants. In modern agriculture systems however, the nutrient solutions are mostly deficient in bioavailable silicon.
As is known (Epstein, E (1999). Silicon. Ann Rev Plant Physiol. Plant Mol. Biol. 50:641-64.), silicon is beneficial for hardening the roots of plants, and is also beneficial or even essential for good plant growth and disease resistance. Leafs are strengthened through an outer opal layer, built of silicic acid polymers acting as a mechanical barrier. Silicon also connects plant substances such as sugars, proteins or phenolic compounds which are present in all kinds of plant fibres. Mycelia of fungi cannot penetrate the plant anymore: Silicon is essential against biotic and abiotic stresses: it increases the yield, induces resistance to stress, controls diseases and pests, reduces toxicity of certain minerals as manganese and aluminium, increases tolerance to freeze calamities, regulates water consumption and improves leaf erectness, resulting in photosynthesis enhancement.
Boron is also an essential nutrient for plants. The combination of boron and silicon show synergistic or antagonistic effects on plant growth and disease resistance, dependant of their concentrations (Bengsch, E(1989). Reduction in symptom Expression of Belladonna Mottle Virus Infection on Tobacco Plants by Boron Supply and the Antagonistic Action of Silicon: Verlag Zeits Naturf. D-7400 Tubingen 0341-0382/89/0900-0777 and Bengsch, E(1989). Effects of simultaneous supply of Silicon and Boron on Plant Growth and on Herbicide toxicity: Verlag Zeitschrift Naturf. D-7400 Tubingen 0341-0382/89/0900-0781). The right concentrations of both nutrients induce synergistic effects on the increase of yield and an increased resistance to diseases and pests.